Historically, livestock waste, particularly in solid form, has been spread on the surface of the soil by a manure spreader using a flail to fling the material to the rear. A more modern side-discharge spreader also deposits the material on the surface of the soil.
The advent of confinement systems for animals which include pits below the confinement area produces a large amount of animal waste in a slurry form which must be handled and disposed of. Typically, the slurry is pumped in a large tank carried by a wagon, but originally it was for the most part, spread or sprayed on the surface of the soil.
This procedure has, as a principal objection, a strong odor which remains after the waste is spread. Moreover, surface spreading of animal waste is not desirable with the potential runoff of nitrates and phosphorus into rivers and streams. This is objectionable because livestock waste is high in nitrogen, and swine waste is also high in phosphorus and with increasing concern with the quality of drinking water, this procedure is becoming less and less acceptable.
Various methods have been proposed for depositing the slurry underground. One method is to use a fertilizer knife, such as shown in U.S. Pat. No. 4,592,294 and to weld a large pipe to the rear of the knife to deliver the slurry behind the knife and into the slot cut in the soil by the knife. This leaves a very narrow band of fertilizer having a high concentration of nitrogen and other nutrients.
Another method of subsoil delivery of animal waste employs a standard chisel plow shank with an attached wide cultivator sweep, in an attempt to distribute the slurry further laterally and to avoid the concentration which occurs in the case of a simple fertilizer knife, described above.
This method, however, presents still another problem—namely, the cultivator sweep unnecessarily tills the soil and may result in burying surface residue. This may be a separate problem, particularly for farmers whose land may have been designated HEL, because there are federal requirements to maintain a certain percentage of crop residue on the surface of such soil. Both the chisel plow shank (which is a wide shank) and cultivator sweeps are designed to create a plowing action that mixes the soil with the residue, buries a large percentage of the residue, and leaves a furrow of exposed liquid behind the shank.
A more recent improvement is disclosed in U.S. Pat. No. 5,865,131. This device uses a spring-cushioned coulter running ahead of the applicator for cutting an initial slot in the residue and providing a break line in the soil to be parted by a trailing shank. The shank spreads the initial slot and deepens it. The shank includes a shoe provided with a pair of wings extended laterally. The shoe is in the form of a tillage point which fractures and lifts the soil in front of the shank. The wings lift the soil laterally of the shank from the center toward the outward ends of the wings to provide slots for promoting lateral distribution of the slurry.
The applicator of the '131 patent is suitable for delivering higher application rates of slurry, in the range of 9,000 to 10,000 or more gallons per acre. However, the ground speed of the '131 patent is limited to a range of 3-5 miles per hour. At these slower speeds, the soil is lifted sufficient to form lateral fissures in the soil at a depth of approximately 5 to 6 inches which permits the slurry to flow laterally of the applicator shank. Any greater speed would cause too much soil disruption, lifting and redistribution (i.e. tillage) due to the use of a forward portion of the shoe which acts like a plow point, having a surface which is inclined upwardly and rearwardly for fracturing and lifting the soil in front of the shank. Another recent improvement is disclosed in U.S. Pat. No. 6,973,884.
The rotary liquid slurry injector of the present invention requires less horsepower and results in a much more desirable flow of heavy residue. It provides excellent residue flow for 24 hour operation, including dew-soaked residue.